Since the first isokinetic machine was invented there has been a lot of hype regarding it’s uses in the medicolegal arena. At long last there was a way of testing a muscle/limb/joint performance and scientifically analysing the results. If we ignore all of the methodological problems with isokinetic testing the interpretation of the results can be a mine field.

At some point you may have to ‘back up’ your opinions and isokinetic testing can be excellent for this. A more contentious type of isokinetic analysis is that used to describe whether or not a subject has as much impairment as they claim.

Some of the many and varied issues related to this are listed next:-

MAP Curve reproducibility:

This has been used in court to describe sub-maximal efforts during testing. However this does not give a clear yes/no answer so this type of interpretation should be avoided.

Coherence of results:

This describes the consistency of the results obtained. At the moment this type of testing has gained a lot of support. It is used in a lot of back testing systems but it has NEVER been fully tested in court. The results obtained tend to point to psycho/musculoskeletal problems.

Sincerity of effort:

(SOE) this combines consistency of curves with coherence of results, symmetry (bilateral usually) and specificity of performance (can you lift X). As you can probably guess this is not open for accurate statistical interpretation.

 

Sincerity of Effort

Consistency:-

There is a maximal effort that can be exerted on each individual test. This does not change in the short term. Especially not during a single session.

The use of consecutive testing usually reveals a series of overlaps, however, this is not always the case. Statistics are often employed to calculate the variance (remember curves don’t always overlap!). There is not one agreed form of statistical measurement.

The ability and legitimacy of dissociating maximal from non maximal contraction is controversial. Hazard et al (1988) say it can be done whilst Newton & Waddel (1993) say it can’t be done (remember they both looked at lumbar spine testing).

Compatibility:-

In concentric testing the strength is inversely proportional to the velocity.

Eccentric strength is normally higher than concentric.

Symmetry:-

Self explanatory e.g left to right (do not use symmetry across a joint e.g. shoulder int/ext rotators).

Specificity:-

Remember to make the test specific i.e. if the subject has a repetitive job don’t ask them to perform a maximal test.